The net utilization of ammonium nitrogen by the growing rat.

While it is well known that ruminants (with the aid of rumen microorganisms) can utilize ammonium salts and urea in lieu of dietary protein,” 2 it has long been held that monogastric animals cannot.’ In view of the findings of Foster, Schoenheimer, and Rittenberg3 that dietary ammonium N15 is rapidly incorporated into rat tissue proteins, it seemed possible that the nitrogen of ammonium salts might be utilized to replace that of the ‘Lnon-essentia1”4 amino acids. This possibility has been tested with rats fed low levels of the essential4 amino acids.